summation values in structure in matlab

问题

I have a 3-by-3-by-3 struct, struct, with fields bit. In each field I have two values. I want to divide values of each field by a summation of values of each field in dimension 3

for example if

struct(1,1,1).bit=[2, 3]

struct(1,1,2).bit=[4, 5]

struct(1,1,3).bit=[6, 7]

my new struct values must be for example:

newstruct(1,1,1).bit=[2/(2+4+6) ,  3/(3+5+7)]

newstruct(1,1,2).bit=[4/(2+4+6) ,  5/(3+5+7)]

newstruct(1,1,3).bit=[6/(2+4+6) ,  7/(3+5+7)]

回答1:

As it is MATLAB, you should possibly go with an nD array instead of the struct. Yet, if you still want to do it this way, don't fear the good old for-loop:

for d1 = 1:size(in,1)
    for d2 = 1:size(in,2)
        d3sum = sum(cat(1,in(d1,d2,:).bit),1);
        for d3 = 1:size(in,3)
            out(d1,d2,d3).bit = in(d1,d2,d3).bit./d3sum;
        end
    end
end

回答2:

I think the only way to do this is with a for loop, or to use nD arrays:

s(1,1,1).bit = [2 3];
s(1,1,2).bit = [4 5];
s(1,1,3).bit = [6 7];

[m,n,p] = size(s);
[mm,nn] = size(s(1,1,1).bit); % assume all elements of the structure have the same dimension
struct_sum = zeros(1,nn);

% compute the sums
for k=1:p
    struct_sum = struct_sum+s(1,1,k).bit;
end

% create the new stucture
for k=1:p
    s1(1,1,k).bit = s(1,1,k).bit./struct_sum;
end

UPDATE: option with nD array

s(1,1,1,1:2)=[2 3];
s(1,1,2,1:2)=[4 5];
s(1,1,3,1:2)=[6 7];
s1 = s./sum(s); % you can specify sum(s,3) to sum along the 3rd dimension - you may also need to use squeeze(...) to remove unnecessary dimensions

Check it gives the correct results:

>> s1(1,1,:,1)
ans =

ans(:,:,1) =  0.16667
ans(:,:,2) =  0.33333
ans(:,:,3) =  0.50000

>> [2 4 6]/12
ans =

   0.16667   0.33333   0.50000

>> s1(1,1,:,2)
ans =

ans(:,:,1) =  0.20000
ans(:,:,2) =  0.33333
ans(:,:,3) =  0.46667

>> [3 5 7]/15
ans =

   0.20000   0.33333   0.46667

来源：https://stackoverflow.com/questions/27961332/summation-values-in-structure-in-matlab

标签

matlab

structure

dimension